Benzothiazole pyrazole containing emissive azo dyes decorated with ESIPT core: Linear and non linear optical properties, Z scan, optical limiting, laser damage threshold with comparative DFT studies

摘要

Positional isomers of "benzothiazoles-pyrazole based azo dyes containing separate with ESIPT core" are analyzed for their "linear and non-linear optical (NLO)" properties. Dyes are emissive in ACN having Stokes shift in the range of 75 nm. Spectroscopic properties are further utilized to calculate band gap by CV. Band gap obtained by DFT and cyclic voltammetry (CV) are in good agreement with each other. Vertical excitation in six different functionals is compared with experimental absorption maxima. Nonlinear absorptive coefficient (beta), nonlinear refractive index (eta(2)), third-order non-linear optical susceptibility (chi(3)) and optical limiting (OL) in acetone, ethanol and DMSO are obtained using Z-scan technique and results are appreciable than previously reported dyes. Satisfactory laser damage threshold (LDT) values are in the range of 7.9-9.7 x 10(13)W/m(2). TGA study indicates that these compounds are useful in several high-temperature processes in the construction of electronic and optical devices. The geometry of the dyes are optimized at "B3LYP/6-311 + G (d,p) level". "Molecular Electrostatic Potential" (MEP), "Frontier Molecular Orbitals" (FMO) are presented using "Density Functional Theory (DFT)" to gain structural insights. Relatively new electrophilicity descriptor- "Hyperhardness" for both the molecules are calculated which suggests the stability of molecules. Global hybrid (GH) functional (B3LYP, BHandHLYP) and range separated hybrid (RSH) (CAM-B3LYP, omega B97, omega B97X, and omega B97XD) functional are used to calculate linear and NLO properties. omega B97 is a more suitable functional observed for determining beta(o) and gamma. Direct relation in-between "dipole moment" (mu) and "linear polarizability" (alpha) is also presented. These dyes can emerge as attractive NLOphores in optoelectronic applications. (C) 2019 Elsevier B.V. All rights reserved.